Higher levels of vitamin C from the diet may reduce
the loss of bone mineral density in elderly men, says a new study from the US.

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But higher intakes of the vitamin from supplementsmay only have a beneficial effect on the bone health of male smokers, according to findings published in the new issue of the Journal of Nutrition.

"Consistent with previous findings of protective effects of fruit and vegetables, we observed protective associations between vitamin C intake and four year change in [bone mineral density of the hip] among men with low calcium or vitamin E intakes," wrote the study authors, led by Shivani Sahni from Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University.

"The dietary rather than the supplement component of vitamin C intakes appeared most strongly protective against bone loss."

The study highlights the importance of vitamin C intake in the diet to maintain bone health amongst men. No association between vitamin C intakes and bone mineral density was observed in women.

Osteoporosis is estimated to affect about 75m people in Europe, the USA and Japan. According to the International Osteoporosis Foundation, the total direct cost of osteoporotic fractures is €31.7bn in Europe, and $17.bn in the US (2005 figure).

The majority of studies into osteoporosis have focused on women since elderly females are four times as likely to develop osteoporosis as their male counterparts.

Study details

The Tufts researchers, in collaboration with scientists from the Institute for Aging Research, Hebrew SeniorLife and the Harvard Medical School, and Boston University School of Public Health, used data from 334 men and 540 women (average age 75) participating in the Framingham Osteoporosis Study. Dietary intakes were assessed using a 126-item food frequency questionnaire in 1988-89.

Bone loss was assessed in 213 men and 393 women at the hip, spine and arm using a dual-photon absorptiometer at the start of the study, and dual X-ray absorptiometry at the four-year follow-up period.

Sahni and co-workers report that total and supplemental vitamin C intakes were related to the bone mineral density (BMD) of the upper part of the hip bone (trochanter), but only amongst male smokers.

Amongst non-smokers, the researchers observed a relationship between total vitamin C intake and the BMD of the neck of the hip bone (femoral neck).

An association with total vitamin C intake was also observed in all men - smokers and non-smokers – if calcium or vitamin E intakes were low. A higher intake of the vitamin from dietary and supplementary sources was associated with less bone loss over the four years of the study, reported the researchers.

"These results suggest a possible protective role of vitamin C for bone health in older men," they concluded.

Protective mechanism

Sahni and co-workers state protective effects of vitamin C for bone health could be expected since the vitamin could counter the effects of oxidative stress, which plays a role in weakening of the bone by resorption.

Furthermore, vitamin C plays an important role in the formation of collagen, which constitutes 90 per cent of the bone matrix.